In general, a dishwasher is an appliance that washes dishes, cookware, etc. (hereinafter referred to as an “object to be washed”) by removing foreign substances such as food waste from an object to be washed using a detergent and water, e.g., water for washing the object.
Typically, a dishwasher includes a tub defining a washing compartment, a dish rack provided in the tub, in which an object to be washed is accommodated, a spray arm for spraying wash water to the dish rack, a sump for retaining wash water, and a supply passage, through which the wash water retained in the sump is supplied to the spray arm.
Recently, a dishwasher capable of spraying wash water evenly toward an object to be washed through rotation of the spray arm has been developed. Further, in order to improve washing performance, the spray arm is structured such that a portion thereof performs a reciprocating movement (rolling) along a predetermined circular arc path using the rotating force of the spray arm.
Referring to FIG. 1, a conventional spray arm 110, which is provided in the tub so as to perform rotation and a reciprocating movement, includes a main arm 130, which forms a main body, and an auxiliary arm 150, which is removably mounted to the main arm 130.
The main arm 130 is provided with an auxiliary arm connection unit 170 at a portion thereof. The auxiliary arm 150 is removably inserted into the auxiliary a in connection unit 170 so that the auxiliary arm 150 evenly sprays wash water while performing a reciprocating movement along a predetermined circular arc path.
The auxiliary arm connection unit 170 includes an extension pipe 172, which extends from the main arm 130, a shaft 176, which extends from the extension pipe 172 and is inserted into the auxiliary arm 150, and a sealing member 700, which protrudes from the outer circumferential surface of the extension pipe 172 in order to prevent the wash water, discharged from the extension pipe 172, from flowing backward to the outer circumferential surface of the extension pipe 172.
Since the sealing member 700 protrudes from the outer circumferential surface of the extension pipe 172, a load generated by the auxiliary arm 150 is concentrated on the sealing member 700. In addition, a load generated by the supply of wash water is also concentrated on the sealing member 700, and frictional force that is generated when the auxiliary arm 150 rotates is exerted on the sealing member 700.
Therefore, the sealing member 700 is worn down. Specifically, the upper portion and the lower portion of the sealing member 700, on which the load is concentrated, are severely worn down.
Such partial abrasion of the sealing member 700 may cause deterioration in a function of preventing backflow of the wash water and may cause tilting of the auxiliary arm 150.
Therefore, a conventional dishwasher has a problem in that wash water flows backward through the worn portion of the sealing member 700, the pressure and the quantity of wash water supplied to the auxiliary arm 150 are decreased, and consequently the washing force is decreased. In addition, since the auxiliary arm 150 is not maintained at a normal position, washing efficiency is deteriorated.